The present invention relates to an adjustable device for exhaustion and/or supply of gases and gas supported particles, said device comprising at least one exhaustion and/or supply conduit which is pivotable in at least vertical direction, whereby a force producing balancing device is provided for balancing the exhaustion and/or supply conduit.
U.S. Pat. No. 3,818,817 relates to an adjustable device for exhaustion of fumes from working places. This device comprises an exhausting conduit which is adjustable in vertical direction for setting thereof in various operating positions. A force producing device in the shape of tension springs is provided to balance the exhausting conduit such that it maintains the positions set.
A problem with this and other balancing devices for adjustable devices of said type is that said balancing devices do not produce balanced forces corresponding with the actual balancing need. This means that one must use friction links which provide sufficient friction for maintaining the conduit in all positions set. A drawback with friction links providing sufficient friction for maintaining the conduit in said positions is however, that a large frictional effect must be overcome when the conduit is pivoted in vertical direction, which means that it is heavy to manipulate.
The object of the present invention is among other things to ensure that in adjustable devices of the abovementioned type, the balancing device produce balanced forces which correspond with the correct balancing need. This is arrived at according to the invention by providing the abovementioned device with the characterizing features of claim 1.
By means of said characterizing features an easily controllable conduit is provided, which maintains substantially all its set positions without needing friction links therefor, producing great friction forces for this maintenance.